Microelectronic circuit packages are prepared in various sizes. One packaging level includes semiconductor chips containing multiple microcircuits and/or other components. Such chips are usually made from semiconductors such as silicon, and the like. Intermediate package levels (i.e., “chip carriers”) comprising multi-layer substrates may include a plurality of chips. Likewise, these intermediate package levels can be attached to larger scale circuit cards, motherboards, and the like. The intermediate package levels serve several purposes in the overall circuit assembly including structural support, transitional integration of the smaller scale circuits to larger scale boards, and the dissipation of heat from the circuit components. Substrates used in conventional intermediate package levels have included a variety of materials, for example, ceramics, fiberglass reinforced polyepoxides, and polyimides.
In order for the aforementioned substrates to have sufficient rigidity, they usually have to be used at thicknesses exceeding 100 microns to provide structural support to the circuit assembly. Also, the aforementioned substrates typically have thermal coefficients of expansion much different from that of the microelectronic chips attached to them. As a result, failure of the circuit assembly after repeated use is a risk due to the failure of joints between the layers of the assembly.
It would be desirable to provide a thin circuit assembly with improved thermal and structural properties that overcome the drawbacks of the prior art.